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Biochem Exam 4 > Cell Cycle Control and Cell Division > Flashcards

Cell Cycle Control and Cell Division Flashcards

1
Q

Extracellular signal that suppress programmed cell death (apoptosis)

A

Survival factors

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2
Q

Activation of the Cyclin-Cdk complex is prerequisite for ______, however the activity of each complex is finely regulated by additional mechanisms

A

downstream events

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3
Q

Each _____ is important for determining which specific targets are subsequently phosphorylated by the Cdk subunit.

A

cyclin partner

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4
Q

Cdk-Activating kinase

A

CAK

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5
Q

The cell-cycle control depends on _______ regulation

A

transcriptional

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6
Q

In the absence of cyclin, Cdk is in an ____ state.

A

inactive

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7
Q

E2F proteins are inhibited by an interaction between E2F and the _____

A

retinoblastoma protein (Rb) family

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8
Q

protein involved in cell cycle regulation.

A

Rb: retinoblastoma protein

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9
Q

Where are the 3 checkpoint controls of cell cycle?

A

Late G1 or Start Checkpoint; G2-M Checkpoint; Metaphase to anaphase transition

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10
Q

The concentrations of the _____ oscillate during the cell cycle

A

three major cyclin proteins

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11
Q

______ causes proteolysis that works to degrade gemenin

A

APC/C

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12
Q

APC/C activity changes during the cell cycle due to its interactions with _____ in anaphase and ____ from late mitosis through early G1.

A

Cdc20; Cdh1

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13
Q

____ is a CKI family member that binds to the active cyclin-Cdk complex.

A

p27

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14
Q

The ______ system is designed to block progression through each of the checkpoints if problems are sensed

A

cell cycle control system

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15
Q

T/F: Just as mutations that alter cyclin or Cdk function can lead to misregulation of the cell cycle, so too can mutations that disrupt any of these regulatory mechanisms create the possibility that a cancer of some type may occur.

A

True

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16
Q

the process by which sister chromatids of duplicated DNA are separated and divided into daughter nuclei. Know the various phases of the mitosis and what happens during each.

A

Mitosis

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17
Q

______ of proteins is a key step in the initiation of many proteins “marked” for degradation by the proteasome complex.

A

Ubiquitylation

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18
Q

Cdk inhibitor protein

A

CKI

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19
Q

Ubiquitin ligase like APC/C;Contains 3 subunits; Ubiquitylates Cdk inhibitor (CKI) proteins in late G1 such as p27.

A

SCF

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20
Q

_____ phosphorylates the Rb protein, rendering it inactive and reducing its binding to E2F. This frees E2F to activate expression of its target genes.

A

G1-Cdk

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21
Q

The _____ binds exclusively to deacteylated histone H4

A

dREAM complex

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22
Q

ubiquitin ligase involved in cell-cycle control; named after its three subunits.

A

SCF

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23
Q

_______ Triggers the events that occur in each phase of the cell cycle; Ensures the proper timing, order and fidelity of the events; Responds to intracellular and extracellular signals; Arrests the cycle whenever the cell fails to complete and essential cell-cycle process or encounters unfavorable intracellular or extracellular conditions

A

cell-cycle control system

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24
Q

During ____ 2 sets of daughter chromosomes arrive at the poles of the spindle and decondense; a new nuclear envelope reassembles around each set; division of the cytoplasm begins with contraction of the contractile ring

A

telophase

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25
Q

genes that turn on and turn off dependent upon cues from environment, hormones, etc., that need to be present in the cell.

A

Inducible gene expression

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26
Q

induces assembly of the mitotic spindle, chromosome condensation, promotes breakdown of the nuclear envelope, rearrangements of the actin cytoskeleton and the Golgi apparatus

A

M-Cdk

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27
Q

The 2nd checkpoint allows the cell cycle to continue if what happens?

A

If environment is favorable and all DNA is replicated

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28
Q

Degradation of the _____ cyclins leads to inactivation of the Cdks.

A

S- and M-

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29
Q

The ______ triggers the major events of the cell cycle

A

cell-cycle control system

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30
Q

During ___ chromosomes are aligned at the equator of the spindle, midway between the spindle poles

A

metaphase

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31
Q

One of the key functions of G1-Cdk is to activate the______ that are themselves gene regulatory factors

A

E2F proteins

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32
Q

Prenatal growth retardation dealing with the ESCO2 gene

A

Roberts syndrome

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33
Q

Extracellular signal that stimulate cell division mainly by stimulating G1/S-Cdk activity that inhibit intracellular negative controls that block progression through the cell-cycle.

A

mitogens

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34
Q

____ is activated in mid-mitosis and remains active in G1, which provides a period in which Cdk is inactive

A

APC/C

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35
Q

_____ starts abruptly with the breakdown of the nuclear envelope; chromosomes can now attach to spindle microtubules via their kinetochores and undergo active movement

A

Prometaphase

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36
Q

If chromosome is unattached to spindle, what halts cell cycle?

A

APC/C

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37
Q

Generally occurs due to a lack of growth factors or nutrients; Occurs in cells when they reach maturity; i.e become terminally differentiated, such as nerve cells, heart muscle cells and bone osteocytes.

A

G0 phase

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38
Q

Cells can remain in G0 for _____ or longer before resuming proliferation

A

days to weeks

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39
Q

family of proteins that regulator Cdk activity

A

Cyclin

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40
Q

S-Cdk, M-Cdk, and G1/S-Cdk inhibit the progression of cell cycle in presence of _____

A

DNA damage

41
Q

is involved in protecting the protein linkages that hold the sister chromatids together; degradation leads to activation of a protease that then separates the sisters and unleashes anaphase

A

Securin

42
Q

The cell-cycle control system depends on ______ events

A

cyclical proteolytic

43
Q

T/F: Cyclin gene expression is regulated and specific cyclins genes are induced (turned on) as the cell cycle transitions from one phase to the next

A

True

44
Q

Gene which encodes an acetyltransferase important for the formation of the cohesion complex that binds to chromosomes and creates cohesion between sister chromatids; mutations lead to decreased rDNA transcription and decreased protein synthesis

A

ESCO2

45
Q

The appearance and disappearance of the various _____ are critical for determining the transitions from one phase of the cell-cycle to the next.

A

cyclins

46
Q

Binding of the specific cyclin to its cognate cyclin-dependent kinase leads to a movement of the T-loop away from the active site, leading to ______

A

partial activation

47
Q

What are the 3 extracellular signals controlling cell division?

A

Mitogens, growth factors, and survival factors

48
Q

Abrupt increases in ____ activity at the G2-M checkpoint drives entry into mitosis and the events of early mitosis

A

M-Cdk

49
Q

Cells enter G0 from a cell-cycle checkpoint in the ____ phase

A

G1 phase

50
Q

_____ interact with cell surface receptors to trigger multiple intracellular signaling pathways

A

Mitogens

51
Q

When the G1/S-Cdks are activated in late G1, APC/C is _____

A

turned off

52
Q

____ associated co-activators promote transcription

A

E2F

53
Q

Loss of the ____ means that their targets can be dephosphorylated by various phosphatases that are present in anaphase, which completes M phase.

A

Cdks

54
Q

____ associates with an F-box protein that is required for binding to specific protein targets

A

SCF

55
Q

_____ checkpoint insures that all of the DNA has been properly replicated

A

The G2-M checkpoint

56
Q

prereplication complex assembles at the origins of replication at what point?

A

Late mitosis-early G1:

57
Q

T/F: Many of the genes (proteins) involved in cell-cycle regulation are critical determinants of cancer progression.

A

True

58
Q

DNA replication occurs at specific sites called _____

A

origins of replication

59
Q

The first checkpoint allow the cell cycle to continue if what happens?

A

If environment is favorable

60
Q

cell-division-cycle genes; important in cell cycle checkpoint control

A

Cdc

61
Q

____ represents a resting or quiescent state in cell cycle

A

G0

62
Q

_____ is essentially inappropriate proliferation

A

Cancer

63
Q

____ can then phosphorylate the T-loop at a threonine residue in the T-loop resulting in full activation of the cyclin-Cdk.

A

Cdk-activating kinase (CAK)

64
Q

The complexes are also regulated by various ______, which provide information about the extracellular environment, DNA or cell damage and whether each step in the cell-cycle has been properly completed

A

inhibitory mechanisms

65
Q

As the cell cycle proceeds a series of _______ insure that each phase is complete before the next one begins.

A

of transitions or checkpoints

66
Q

2 additional proteins ___ and _____ assist in the addition of multiple ubiquitin molecules to the CKI and this targets the protein for degradation in the proteasome complex

A

E1 and E2

67
Q

During ____ the sister chromatids synchronously separate to form 2 daughter chromosomes and each is pulled slowly toward the spindle pole it faces; kinetochore microtubules get shorter and the spindle poles also move apart; contribute to chromosome segregation

A

anaphase

68
Q

____ is thought to promote cell cycle entry by increasing the expression of the genes encoding the G1 cyclins (D cyclins), which results in increased G1-Cdk (cyclin D-Cdk4) activity

A

Myc

69
Q

In the inactive state the catalytic or active site of the cyclin-dependent kinase is blocked by the presence of a region called the ______

A

T-loop

70
Q

protein complex bound to origin of replication sites in DNA

A

ORC: origin recognition complex:

71
Q

(genes that are turned on very early or almost immediately after a mitogen binds to its receptor)

A

immediate early gene expression

72
Q

The 3rd checkpoint allows the cell cycle to continue if what happens?

A

If all chromosomes are attached to the spindle

73
Q

T/F: Cells can enter G0 permanently until the cell dies

A

True

74
Q

The activity of cyclin-Cdk is further regulated by _____, which further phosphorylates Cdk and renders it inactive and by Cdc25 phosphatase that dephosphorylates and restores activity

A

Wee1 kinase

75
Q

Extracellular signal that stimulate cell growth (increase in cell mass) by stimulating protein synthesis and inhibiting protein degradation

A

Growth factors

76
Q

Where does the 2nd checkpoint of cell cycle occur?

A

G2/M

77
Q

Cytoplasm is divided in 2 by a contractile ring of actin and myosin filaments which pinches the cell in 2 to create 2 daughters, each with 1 nucleus

A

cytokinesis

78
Q

What are the phases of mitosis

A

Prophase, Prometaphase, Metaphase, Anaphase, and Telophase

79
Q

The cell cycle checkpoint control system depends on cyclically activated _____

A

cyclin-dependent protein kinases (Cdks)

80
Q

The concentrations of the ____ do not change (constitutive expression)

A

Cdk

81
Q

How many checkpoints or the cell cycle are there?

A

3

82
Q

regulatory transitions in the cell-cycle in which the cell cycle will be arrested unless specific prior biochemical events are fully completed

A

Cell cycle checkpoints

83
Q

Cyclin-dependent kinase (Cdk) requires the binding of ____ and subsequent specific phosphorylation to become an active enzyme

A

cyclin

84
Q

anaphase promoting complex or cyclosome

A

APC/C

85
Q

Passage through the Start Checkpoint in late G1 launches ____ and __ phase of cell cycle

A

DNA replication and the S phase of the cell cycle.

86
Q

The cell-cycle involves DNA replication and dividing the cell to create ______

A

two identical daughter cells

87
Q

In addition, the _______ initiates the metaphase to anaphase transition.

A

Anaphase-Promoting Complex or Cyclosome (APC/C)

88
Q

family of protein kinases involved in the control of the cell-cycle

A

Cyclin-dependent kinases (Cdks)

89
Q

genes that are expressed at a constant level throughout the life of a cell.

A

Constitutive gene expression

90
Q

The expression of the 3 major cyclin proteins is _____

A

induced

91
Q

During _____, the replicated chromosomes each consisting of 2 closely associated sister chromatids condense

A

prophase

92
Q

complex of proteins involved in cell cycle control arrest and senescence by binding to the E2F family of transcription factors.

A

dREAM

93
Q

Where does the 3rd checkpoint of cell cycle occur?

A

In M phase between Metaphase and Anaphase

94
Q

Each _____ can induce different effects at different times in the cell-cycle based upon the relative presence, absence or abundance of each specific target, which can change depending upon the phase of the cell cycle.

A

cyclin-Cdk

95
Q

The first checkpoint of the cell cycle occurs at what point?

A

G1/S phase

96
Q

Member of the ubiquitin ligase family of proteins; Catalyzes the ubiquitylation and degradation of securin and the S- and M-cyclins.

A

APC/C

97
Q

____ binds to both the cyclin and the Cdk subunits. This distorts the active site of the Cdk and also inserts into the ATP-binding site, further inhibiting the enzyme activity

A

p27

98
Q

The central component of the control system is the series of _____ that regulate transitions through the various phases

A

cyclin-Cdk complexes

99
Q

____ and ___ lead to histone modifications that result in histone compaction and suppression of gene expression

A

E2F and pRB

Biochem Exam 4 (6 decks)

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